1. Field of the Invention
The present invention relates to a nitride semiconductor device used in electric power control and, more particularly, to a horizontal nitride power FET.
2. Related Background Art
A power semiconductor device such as a switching device or a diode used for power control is used in a circuit for a switching power supply, an inverter, or the like, and such power semiconductor device is required to have a high breakdown voltage and a low ON-resistance.
There is a trade-off between the breakdown voltage and the ON-resistance of the semiconductor device, depending on device material.
In a power semiconductor device using silicon as a general device material, a marginal low ON-resistance has been realized by the progress of engineering development up to now.
Therefore, in order to further reduce the ON-resistance of a power semiconductor device, a device material must be changed, a wide-band gap semiconductor including a nitride semiconductor such as gallium nitride (GaN), aluminum gallium nitride (AlGaN), or silicon carbide (SiC) is used as a switching device material to make it possible to improve the trade-off determined by a material, and an ON-resistance of the device can be dramatically made low.
At the present, the study of a power semiconductor device using a wide band gap semiconductor is actively performed. Though a nitride semiconductor device such as gallium nitride (GaN) realizes a low ON-resistance, it is not designed in consideration of the characteristics of a power semiconductor device such as an avalanche withstanding capability. This is because a gallium nitride (GaN) based device is designed on the basis of a communication device.
Some semiconductor devices using gallium nitride (GaN) as a device material have been proposed and publicly known. For example, see Japanese Patent Application Laid-Open No. 2001-168111.